Mostly WWI to early interwar, with minimal borrowing WWII. I think the idea was to stay very clear of typical mid to late WWII tanks, really, safe perhaps for the T-xx soviet tank turret.
I'm not too sure about the B1 but for the nested gun at the front.
However, like two months ago, I stumbled upon a 40K fan's page of custom made B1-inspired IG tanks. It was very well done.
Now, trying to find that damn page again, I found another one, and I see some people had fun with a B1 model.
http://www.dakkadakka.com/dakkaforum/po ... 29805.page
Baneblade turret was quite overdone on that chassis, so Dhugs made a modification and found a more appropriate piece. It really looked ace.
There's quite something truly awesome to the
wreck of that B1. It's almost medieval in aspect. It's almost asking for an excuse to have two paired giant saw-wheels mounted at the front of that monster.
The Char-B has quite a f***ton of potential as a lost STC stylized IG tank.
Check out
this file. Add some sponsons are you're done.
EDIT: can't find the damned custom IG tank but here's one that
on topic.